The energy present in a magnetostatic structure has been used in a wide range of applications, such as loudspeakers, microphones, generators, electric guitar pick-ups and the like. The generation of a voltage in a conductor by the changing of a magnetostatic structure or the movement of a magnetostatic structure relative to the conductor is an old concept. These devices in the prior art commonly used a permanent magnet made of electrically conducting metal. Since magnets made of electrically conducting metals rapidly attenuate any electromagnetic energy, as do any electrical conductors, the use of such permanent magnets in conjunction with these various devices has been primarily limited to core elements inside electrically insulated conductor coils or similar applications.
With the advent of ceramic magnetic materials, magnets which are not electrical conductors have become available. Ceramic magnets are available in both permanent (hard) magnetic materials or magnetically soft materials. Various types of ceramic magnetic compositions of both the hard and soft types use "ferrite" materials. Generally these materials are magnetically soft materials (that is nonpermanent magnets). "Hard" or permanent magnet materials are high loss high retentivity, high coercivity materials with low permeability.
The coercive force of hard magnetic materials is on the order of tens of thousands of times greater than that of the lowest coercive force of soft magnetic materials. From a magnetic softness view point, the important thing to regard is the hysteresis loop. For soft magnetic materials the area of the hysteresis loop is quite small, whereas for "hard" magnetic materials the area of the hysteresis loop is large by comparison with soft materials. The bulk of the work in electric circuit design using magnetic materials involves the application of magnetically soft cores in inductors and transformers and the like. These uses encompass a large range of ferrite and metal cores and the applications of permanent magnets (metal or ceramic) in electronic circuit design has been nearly neglected.
Soft ceramic ferromagnetic materials and ferrite materials have been employed as coatings or cores for radio frequency transmitters and receivers to increase the inductance of the antennae which in turn permits reductions in the antennae lengths or sizes. Antennae which have been modified with such soft magnetic materials (high permeability materials) are known, and such antennae systems are disclosed in U.S. Pat. No. 2,748,386 issued May 29, 1956. Since the prior art antennae of the type disclosed in U.S. Pat. No. 2,748,386 rely upon inductive coupling, the high permeability (inductance) available in the soft ferromagnetic or ferrite materials is desired. While some improvements in the operation of antennae systems which are treated with these "soft" magnetic materials do result, the differences between such treated antennae and conventional antennae are not significant.
Antennae for use in conjunction with various types of radio frequency transmitters and receivers are well known. The variety of shapes and electrical configurations of antennae is almost limitless. These range from end-fed antennae, which are substantially linear conductive rods of various lengths having specific relationships to the wavelengths of the frequency of the signals transmitted from or received by such antennae, to complex arrays of components. Helical antennae, as well as composite antennae involving combinations of various antenna shapes and configurations such as complex lens antennae, multiple-tuned antennae, dipoles and the like are well known. The particular configuration which is employed for any specific purpose is selected in order to function properly with respect to the frequencies which are involved and the radiation patterns desired.
Irrespective of the type of antenna or antenna configuration which is employed, all antennae, both transmitting and receiving antennae or those used for both functions, are subject to limitations in the power gain of any given antenna due to what is known as "skin effect". This phenomenon is one of non-uniform current distribution over the cross section of an alternating current conductor. At high frequencies, the current for a conductor is carried only by a thin surface layer of the conductor, the thickness of the layer decreasing with increasing frequency. The result of this phenomenon is a self-induced counter-electromotive force in the conductor which results in considerable cancellation of the received energy and increased effective resistance.
Thus, the gain or power of the antenna, whether it is a transmitting antenna or a receiving antenna, is reduced from the theoretical ideal which it could exhibit if "skin effect" was not present. This means, for a receiving antenna, the capability of the antenna to respond to weak signals is substantially impaired. The signal-to-noise ratio is lowered; and for any given receiver, it is necessary to employ substantially greater gain in the RF stages than would otherwise be necessary for the same reception capabilities if the undesirable effects of "skin effect" were not present. Similar disadvantages result with respect to transmitting antennae, the power of which is substantially impaired by the increased effective resistance produced by skin effect. Thus, for any given transmitted power, the power of the output amplifying stages must be considerably higher than would otherwise be required if "skin effect" phenomenon was not present. As stated above, as the frequency of the carrier signal increases the deleterious effects of skin effect increase proportionately.
As is well known, communications systems in a wide variety of different forms, such as AM radio, FM radio, television, two-way FM communications such as used in citizens' band (CB) radios, police and fire communications networks and the like are in widespread use throughout the world. These communications systems utilize the transmission and reception of electromagnetic radio frequency waves which are radiated through space from a transmitting antenna at the originating source or station to a receiving antenna at the point of utilization. The radio frequency waves extend in frequency from a relatively low 10 kilohertz up into frequencies of hundreds of megahertz. Different portions of this spectrum are divided into different frequency bands allocated to various systems of transmission. The moving electromagnetic radio frequency waves which are radiated through space are created at the transmitting station by coupling the transmitter output to an antenna which has a configuration particularly adapted to the frequency of the transmission and the use or application of the signal in the particular system with which the transmitter and antenna is employed. At the receiving end, a receiver which is used in conjunction with the transmitted signal to receive and convert it to a usable form, such as audio or visual, has an antenna which intercepts the moving electromagnetic waves and converts them to electrical signals which are processed by the receiver.
In conventional antennae, both transmitting and receiving, the antenna itself is what may be termed a "passive" component in the system. At the transmitting end, the alternating current signal creates electromagnetic radiation when it is applied to the antenna. At the receiver, the moving electromagnetic wave is intercepted by the conductive antenna and results in the generation of a corresponding alternating current electrical signal in the conductor which then is applied to the RF amplifier and processing stages of the receiver. These conventional antennae are electrical devices only. The transmitter generates an electrically polarized electromagnetic wave and the receiver responds to the electrical components and resonates with the corresponding electrical polarization of the electromagnetic wave. Because of the "skin effect" mentioned above, at higher frequencies the thickness of the layer of the conductor in the antenna which actually carries the current becomes increasingly thinner and results in an increasing counter-electromotive force. This, in turn, results in increased effective resistance in the antenna and correspondingly greater self-cancellation. Thus, at higher frequencies, the power of an antenna, either a transmitting antenna or a receiving antenna, is substantially lessened by "skin effect".
In order to provide sufficient power, either for transmission or reception, for conventional antennae in any given situation, it often is necessary to have extremely large antenna structures or antenna towers to attain the desired operating characteristics of the transmitter or receiver. Such structures are costly to build; and because of the substantial space they require or the substantial height to which they must reach, result in expensive, cumbersome and unattractive installations. For example, bulky rooftop television receiver antennae are commonly employed in order to provide some measure of reasonable reception for television receivers used in homes. Similarly, two-way radio antennae, such as used for ham radio operators, CB radio base stations, and the like require large unsightly installations if any reasonable range is to be attained from the radio system using the antenna. In addition, mobile antennae used by police cars and CB installations in automobiles and trucks, for maximum effectiveness over a reasonable range, require a relatively long "whip" antenna structure.
It is desirable to provide transmitting and receiving antennae in a variety of configurations which have relatively high power capabilities, minimum size, and which eliminate or substantially minimize the "skin effect" self-cancellation phenomenon ordinarily encountered in antennae structures. In addition, it is desirable to increase the coupling between the coils of a guitar pick-up, speaker, microphone or other devices using coils and magnetostatic energy to improve the operation of such devices.